You finally make your first start for your new club. You are 3-0 up and have been the game’s outstanding performer.

Your final contribution in the first-half is to crash a superb free-kick against the cross-bar which is then bundled into the net for that third goal. The result is not in doubt and you have made your mark; you have arrived. The crowd show their appreciation. This is what it is all about.

And then you are substituted at half-time. Such was Xherdan Shaqiri’s surprising fate for Liverpool during their comfortable victory over Southampton which gave them outright leadership at the top of the Premier League and extended their 100 per cent, perfect start to the season to six wins from six in the league and seven overall.

Except Jurgen Klopp did not see it as comfortable. There were things that the manager did not like. Changes had been made to the team that defeated Paris St-Germain in the Champions League in midweek and there was also an important, experimental shift in formation.

The Liverpool manager wanted to look a 4-2-3-1 line-up with Shaqiri as the No 10, in the middle of that three behind the striker, and as eye-catching as the Swiss international had played Klopp noticed the space afforded to Southampton down the flanks and that Jordan Henderson and Georginio Wijnaldum were in danger of being over-worked as the central midfield pair.

There was mitigation. Liverpool’s attempts to practice that new formation had been curtailed by winds, thunder and even lightning at training on Friday. They could trial it for just seven minutes, apparently.

So James Milner replaced Shaqiri, the formation was reverted to the usual 4-3-3 and Southampton did not have a shot on target until injury-time. Any sign, any flicker, any hope of a comeback or even any meaningful resistance was snuffed out. Liverpool were in total control and that is what the manager wanted. It was not about running riot.

Klopp later said he had spoken to Shaqiri, who still collected the sponsor’s man-of-the-match award, probably a first for a player substituted after 45 minutes for tactical reasons, about his decision.

"I said to Shaq at half-time that I had never brought a player off after such an influential time without an injury. He is not injured. But I wanted to control the game and go back to our normal formation. And that helped, we really controlled it," he explained.

Shaqiri was said to have been subdued when he left the stadium, there was criticism of Klopp from former players but it was a lesson. Shaqiri, the former Bayern Munich and Inter Milan player, wants to play for a top team, having left Stoke City, and this is what it is all about. He is big enough to deal with it.

The substitution very publicly showed one thing above all else: Klopp’s ruthless professionalism, which has always been there but is now coming to the fore, can be Liverpool’s most effective weapon this season as they attempt to win a trophy, as they attempt to win the Premier League for the first time in 29 years.

They may not do it – Manchester City rightly remain the favourites – but as discussed in this column last January after they beat Pep Guardiola’s side 4-3 at Anfield in the Premier League, Liverpool should be the team running them the closest; they should be their main challengers. Not just because they are a coming force, not just because of the impressive signings made this year which addressed the significant deficiencies in the team and in the squad – goalkeeper, central defence, central midfield – but because that strengthening and deepening of the pool has given Klopp the mandate to be even more authoritative and, therefore, more ruthless.

He is – and always will be – one of the most emotionally-invested managers and that was shown in the attuned way in which he explained the decision to substitute Shaqiri. That understanding of the value of a shared feel-good factor will always be one of Klopp’s greatest strengths.

But Liverpool are already a different beast this season; a far more formidable beast; a far more ruthless beast. They do not even play quite the same brand of football. It is not really the whirlwind of full-throttle attack that can be so overwhelming but also more loose. It is much more about harnessing that; controlling that. Taking a grip on games and not letting go. Game-management.

In their first six league matches of last season Liverpool scored 10 goals – just four fewer than this season – but collected only eight points. This season they have 18 points. Liverpool’s efficiency is therefore far greater. It is considerably more than a goal for a point while only two goals have been conceded in six league games with four clean sheets.

They now have a double-header against Chelsea – firstly in the Carabao Cup, when Shaqiri is expected to start – and then in the Premier League at Stamford Bridge next Saturday. After that it is a crucial Champions League tie away to Napoli followed by the momentous visit of City the following Sunday. Then there is the international break.

That is a potentially defining sequence of four fixtures in three different competitions and explains, even more, the decision to substitute Shaqiri. Logic would have appeared to suggest it would have made sense to keep him on, given he is not a starter in the strongest XI, but Klopp was preparing for what is to come and drilling into his players the need for that control when ahead.

It is about pressing home that advantage by not giving the opponent any hope whatsoever. It is about being utterly professional and, above all, ruthless in the way Klopp himself has shown.